The delivery of a metered dose of medication via inhalation into the lungs is a common method used for administration of a variety of drugs, including, but not limited to, asthma medications, insulin, steroids and treatments for pulmonary diseases. Although the metered dose inhaler canister dispenses a fixed, metered dose of medication, only a portion of the metered dose actually reaches the lungs of a patient. Even if inhalation is properly timed with the dispensing of the medication from the inhaler, the amount of medication reaching the lungs is inconsistent, depending on various factors including the quantity of medication dissolved and/or entrained in the air entering the patient's lungs, and the quantity of medication that is deposited on one or more surfaces of the inhaler, the mouth and/or oropharyngeal area of the patient. Deposition of medication in the mouth or oropharyngeal area of the patient can cause complications, such as candidiasis, and may leave an unpleasant aftertaste.
Many patients also have practical problems with the use of inhalers, such as difficulty compressing the dose canister, difficulty in timing inhalation with the dispensing of medication, and an inability to inhale a full dose of medication in a single breath. In practice, patients frequently activate an inhaler multiple times in order to dispense a single dose, despite the fact that the desired metered dose should have been dispensed via a single activation of the inhaler. This is a documented response to the difficulty and inconsistency of medication delivery, which response undermines the effectiveness of metered dose inhalers, thereby leading to concerns such as over-medication, under-medication, and waste, as well as higher costs for treatment. The problem with improper storage and difficulty with sterilization techniques also poses risk for further unwanted fungal and bacterial infections.
One proposed solution to the problem of inconsistent dosing has been to provide a “spacer” or “chamber” within the inhalation device, typically in the form of a reservoir of air. The spacer or chamber provides a location for mixing the metered dose of medication with air before inhalation, thereby potentially reducing the inconsistency of dosing due to timing difficulties. U.S. Pat. Nos. 4,470,412; 4,790,305; 4,926,852; 5,012,803; 5,040,527; 5,042,467; 5,816,240; and 6,026,807 disclose various devices of this type.
Additionally, some devices with spacers have been provided with a valve mechanism to permit inhalation of a single dose of medication in more than one breath. For example, see U.S. Pat. Nos. 4,470,412 and 5,385,140. The articles, Demirkan, et al., “Salmeterol Administration by Metered-Dose Inhaler Alone vs. Metered-Dose Inhaler Plus Valved Holding Chamber,” Chest, 117 (2000) pp. 1314-1318, Finlay and Zuberbuhler, “In vitro comparison of beclomethasone and salbutamol metered-dose inhaler aerosols inhaled during pediatric tidal breathing from four valved holding chambers,” Chest, 114 (1998) pp. 1676-1680, and Konig, “Spacer devices used with metered-dose inhalers. Breakthrough or gimmick?” Chest, 88 (1985) pp. 276-284; also provide information in relation to such devices.
For infants or other patients who have difficulty using a mouthpiece, a mask is commonly attached or incorporated onto the inhaler. See U.S. Pat. Nos. 4,809,692; 4,832,015; 5,012,804; 5,427,089; 5,645,049 and 5,988,160. Also, some devices include an audible signaling device to warn patients when inhalation exceeds a desirable rate, e.g. U.S. Pat. Nos. 4,809,692 and 5,042,467.
One method of attaching a spacer to a canister of a metered dose inhaler is to insert the inhaler into a universal adapter such as that shown in U.S. Pat. No. 5,848,588, but this is bulky and awkward to use. Other devices are designed to have a specific canister inserted into the device. It would be beneficial to be able to insert different canisters into a single inhaler.
Accordingly, in view of the foregoing, there remains a need for an easily portable, universal inhaler system that can be easily used and cleaned. There is also a need for a design that permits the use of attachments for infants, if desired. These and other objects of various embodiments of the invention are addressed by one or more of the embodiments of the invention described below. It should be understood, however, that specific embodiments of the invention need not address each and every object listed herein in order to be considered part of the inventive concept.